Electromagnetic metering pump



ELECTROMAGNETIC METERING PUMP Filed Oct. 23. 1967 AOMINISTATDR BY www 'ATTORNEY United States Patent O 3,479,959 ELECTROMAGNETIC METERING PUMP William N. Christensen, deceased, late of Portland, Oreg., by Robert L. Slaughter, administrator, Beaverton,

Oreg. 97005 Filed Oct. 23, 1967, Ser. No. 678,160 Int. Cl. F04b 7/04; H02k 7/14, 35 /02 U.S. Cl. 103-53 5 Claims ABSTRACT F THE DISCLOSURE A pump having an elongate fluid chamber and a piston supported in the chamber for reciprocal movement therein. The piston is resiliently biased so as to Abe sup-ported in the chamber intermediate the ends thereof when in a quiescent state. Disposed in the piston is a tubular body of magnetic material for magnetic cooperation with an electromagnetic coil surrounding the chamber. The coil is asymmetric of the quiescent position of the magnet, so that energization of the coil will effect movement of the piston relative the chamber.

This invention relates to a pump for delivering fluid and, more particularly, to a pump that delivers a precisely variable and controllable quantity of fiuid at the outlet of the pump.

An object of the present invention is to provide a pump wherein the output delivery rate thereof is directly proportional to the magintude of alternating current signal applied thereto. A pump capable of achieving this object is to be contrasted with certain other precision fluid delivery devices which require conversion of a feedback signal to some other form of energy, for example, mechanical energy used to rotatably position a valve stem or the like. This object is achieved by providing a pump that includes a permanently magnetized piston which piston is located in an electrically induced magnetic field. The strength of the field is proportional to the magnitude of the current. Because the output delivery rate of the pump is directly proportional to the strength of the magnetic field, and because the strength of the magnetic field is proportional to the magnitude of the current, the output rate of the pump is proportional to the magnitude of the current.

Another object is to provide a pump that can readily be adjusted to various maximum fluid delivery rates. This object is achieved by providing a pump that can be quickly disassembled and by providing an internal spacer that can be changed during disassembly. The thickness of the spacer determines the delivery rate, higher rates being attained as the spacer is made thinner.

Still another object is to provide a pump structure that can be formed of relatively low strength synthetics that are inert to most liquid materials; attainment of this object is effected by the present invention because all parts of the pump are symmetric of a central longitudinal axis. Such construction minimizes stresses on the parts that constitute the pump of the present invention.

These and other objects will be more apparent after referring to the following specification and accompanying drawing, in which:

FIG. 1 is a cross-sectional view at the diameter of a pump according to this invention, the internal parts being in a quiescent state;

FIG. 2 is a simplified version of the pump of FIG. 1, the internal parts being shown near the end of an inlet or loading stroke; and

FIG. 3 is a simplified version of the pump of FIG. 1, the internal parts being shown near the end of an outlet or discharge stroke.

3,479,959 Patented Nov. 25, 1969 ICC Referring more particularly to the drawing, reference 12 indicates a tubular housing that defines a cylindric chamber 14 centrally thereof. Housing 12 is exteriorly threaded at opposite ends thereof to receive an inlet end cap 16 and an outlet end cap 118. The housing and end caps are made of non-magnetic material to permit magnetic communication therethrough.

The end caps are provided with respective openings 20 and 22 for communicating fluid into and out of cylindric opening or chamber 14. Opening 20 has at the interior end thereof a seat 28 that is arranged concentric with opening 20. Mounted Within chamber 14 is a valve ball 30 which is sized to cooperate with seat 28 to prevent fluid fiow between cylinder .14 and inlet opening 20 when the ball is seated in the seat. The walls of chamber 14, at the region thereof adjacent seat 28, have one or more longitudinal excisions 31 so as to permit fluid flow past valve ball 30 when the ball is unseated from seat 28. Also supported in cylindric chamber 14 is a piston 32; the piston is adapted slidably to reciprocate within Vcylindric chamber 14. Piston 32 preferably has an outer diameter so related to the inner diameter of the cylindric chamber that fluid cannot flow around the piston.

Piston 32 defines a central fluid passage 34 that has a reduced throat portion 36 medially thereof. Throat portion 36 includes a seat 38 which cooperates with a valve ball 40 to inhibit flow through the central passage. The walls of passage 34 adjacent seat 38 have one or more excisions 41 so as to permit fluid flow past valve ball 40 when the ball is unseated from seat 38. Ball 40 is urged into fluid sealing engagement with seat 38 by a compression spring 42, the opposite ends of which spring bears against outlet cap 18. A second compression spring 44 is provided between piston 32 and valve ball 30 to bias the latter ball into engagement with seat 28.

Piston 32 is formed with an annular chamber concentric with fluid passage 34, which chamber contains a tubular shaped body of magnetic material 46. The material is retained in the chamber by a ring 48 that is threaded into the right end of the piston. At the rightward extremity of housing 12 is a spacer 50 which, as will appear in more detail hereinafter, can be replaced with a spacer of a different size to effect varying rates of pumping by the apparatus of the invention. It is sufficient for the present to note that the spacer has a bearing surface at the left extremity thereof against which surface piston 32 impinges at the rightward extremity of reciprocal piston movement.

For effecting such movement there is provided exterior of housing 12 in circumscribing relation thereto a coil or winding 52 that has terminal Wires 54 vassociated therewith. The terminal wires are adapted for connection to an alternating current signal of variable amplitude and/or frequency so as to afford variation of the delivery rate of the pump. As can be seen in FIGURE 1, the magnetic material 46 in pist-on 32 is so arranged with respect to coil 52 that the magnetic material is asymmetric of the field when the field first builds up from a quiescent state. This assures rapid actuation upon application of a signal to coil 52.

In operation, the pump of the invention is coupled into a fluid line with the input or reservoir side of the system connected to inlet fitting 20 and the discharge or output side of the system connected to fitting 22. In the quiescent state, or the position shown in FIGURE 1, no fluid is delivered to the outlet fitting because spring 44 retains valve ball 30 in seat 28. When an AC signal is applied to the wires 54, a magnetic field inside of coil 52 is formed and is polarized in such a direction that it interacts with magnetic material 46 to move piston 32 leftwardly. The consequence of leftward movement is that any fluid intermediate valve ball 30 and valve ball 40 will be discharged toward outlet fitting 22 because leftward movement of piston decreases the tension yon spring 42 until valve ball 40 is unseated from the seat 38. No reverse flow is possible because the force that spring 44 exerts in seating ball 30 into seat 28 increases in response to the leftward movement of piston 32.

When the polarity of the AC signal in coil 52 reverses itself, the direction of the magnetic field within the coil experiences a corresponding reversal. Consequently,` piston 32 is driven rightwardly toward a position seen most clearly in FIGURE 3. Rightward movement of piston 32 seats valve ball 40 into seat 38 and releases the force of spring 44 on valve ball 30. Accordingly, the latter valve ball unseats so as to admit liquid from inlet tting 16 into the region on the right-hand side of valve ball 30. Additionally, rightward movement of the piston forces liquid to the right of valve ball 40 out through outlet opening 22. When the polarity of the voltage again reverses so as to drive piston 32 toward the position shown in FIGURE 2 the fluid to the right of the valve ball 30 is forced rightwardly of ball 40.

Spacer 50 limits the rightward movement of piston 32 and, therefore, limits the amount of fluid that is pumped for each cycle of excitation of coil 52. Consequently, the spacer regulates or limits the delivery of fluid. Spacer 50 can be readily removed by unthreading outlet fitting 22 and end cap 18. The thickness of Spacer 50 can be reduced by grinding or another spacer of different thickness can be inserted in its place. Thus, the spacer provides a relatively gross adjustment of the device.

More precise adjustment is effected by appropriately controlling the frequency and magnitude of the alternating current signal supplied to coil 52. For amplitudes less than the amplitude of signal necessary to drive piston 32 into contact with spacer 50, the output rate of the device is approximately directly proportional to the magnitude of the current. Variation in frequency is also active to control the discharge rate of the pump, higher frequencies giving a greater output rate than lower frequencies.

Because there are many prior art systems for generating an alternating current signal that has a frequency or amplitude proportional to uid demand, the pump of the present invention can be expeditiously incorporated into existing systems without complicated feedback links. Only an AC signal having either frequency or amplitude or both frequency and amplitude proportional to uid demand is necessary.

Because of the form of construction employed, the device can be readily disassembled for repair or maintenance such as may be necessary after extended usage. The entire structure can be made of inert synthetics such as Tetion and the like in which case a valve so constructed is capable of pumping in highly precise quantities even the most volatile substances.

Thus, it will be seen that the present invention in its provision of an active reciprocating member controlled' in response to alternating current signal, provides a pump wherein volumetric efliciency is a function of the amount of current passing through the coil. Consequently, the pump can be made to move precisely measured amounts of fluid by regulating the amount of current passing through the coil. Such principle also permits continuous and instantaneous changes in volumetric efficiency over the range of maximum volume to zero volume. The system can be readily incorporated into existing systems by insertion of a suitable current meter which can be calibrated to provide an AC signal proportional to the volume of fluids being demanded by a system. Accordingly, complex instrumentation is avoided without sacrificing accuracy or reproducability of results.

Although one embodiment of the invention has been shown an-d described, it will be obvious that other adaptations and modifications can be made Without departing from the true spirit and scope of the invention.

What is claimed is:

1. A pump comprising a housing defining an elongate cylindric chamber having an inlet at one end thereof and an outlet at the other end thereof, a piston slidably mounted in said chamber and movable toward said inlet in a loading stroke and toward said outlet in a discharge stroke, said piston having a uid passage therethrough, a transfer valve in said fluid passage adapted to arrest fluid ow through said passage during said discharge stroke Y and to permit flow through said fiuid passage during said loading stroke, means including a rst compression spring for resiliently biasing said transfer valve toward the uidarresting position, said spring residing in said fluid passage so as to resiliently bias said piston away from said outlet end when said transfer valve is seated, an inlet valve disposed in said chamber between said inlet end and said piston 'and adapted to cooperate with said inlet end for preventing backflow from said chamber to said inlet opening during said loading stroke, means for resiliently biasing said inlet valve toward said inlet opening, said inlet valve biasing means including a second compression spring residing in said chamber and extending between said inlet valve and said piston so as to resiliently bias said piston toward said outlet end when said inlet valve is seated, said iirst and second compression springs acting to resiliently axially suspend said piston in said chamber between said inlet end and said outlet end, a magnetic body mounted in said piston, means for generating a magnetic field in magnetic communication with the magnetic body and means to periodically vary the magnetic field in polarity and magnitude so as reciprocally to drive said piston through said loading stroke and said discharge stroke.

2. A pump according to claim 1 in combination with a spacer disposed in said cylindric chamber adjacent said outlet end, said spacer limiting the extent of the discharge stroke and being removable for replacement.

3*. A pump according to claim 1 wherein said magnetic eld generating mean-s comprises a wire coil circumscribing said housing, said wire coil being asymmetrically disposed relative said magnetic body when said piston is in a quiescent state.

v4. A pump according to claim 1 wherein said chamber is formed by a cylindric nipple having threaded portions at opposite end-s thereof and end caps threadedly engaged therewith, so that access to the interior of said pump can be readily achieved.

5. A pump according to claim 1 wherein said transfer valve biasing means and said inlet valve biasing means are arranged so as to be compressed alternately in response to reciprocal movement of said piston.

References Cited UNITED STATES PATENTS 2,293,684 8/ 1942 Holthouse 103-53 3,267,866 8/1966 Unger 103-53 ROBERT M. WALKER, Primary Examiner U.S. C1. X.R. 310-18 

